From Ameinfo.com: The Islamic finance industry is plagued by a lack of solid and reliable data. While the causes of this are the subject of much debate, the consequences are that the industry is largely ignorant of how big it is or how fast it is growing.
Estimates of the size of the industry seem to peak around $1,000bn although more conservative estimates indicate that the overall size of the industry is nearer $750bn............Full Article: Source